Ductless Mini-Split BTU Sizing Calculator
Calculate required mini-split heat pump capacity (9k, 12k, 18k, 24k BTU), tonnage, electrical circuit specs, and copper lineset sizing.
Calculated Results
Frequently Asked Questions
How many BTUs do you need per square foot for a ductless mini-split?
In general residential HVAC sizing, plan for approximately 20 to 25 BTUs per square foot of living space for rooms with standard 8-foot ceilings, adjusting upward for vaulted ceilings, large south-facing windows, kitchens (+4,000 BTU), and poor insulation.
What are standard mini-split sizes?
Ductless mini-splits are sold in standardized capacities: 9,000 BTU (3/4 Ton - up to 350 sq ft); 12,000 BTU (1 Ton - up to 550 sq ft); 18,000 BTU (1.5 Tons - up to 800 sq ft); 24,000 BTU (2 Tons - up to 1,200 sq ft); 36,000 BTU (3 Tons - up to 1,800 sq ft).
Why is oversizing a mini-split bad?
An oversized air conditioner cools the room too quickly without running long enough to remove ambient humidity, leaving the room feeling cold and clammy. However, modern variable-speed inverter mini-splits ramp down compressor speeds, making them much more forgiving than single-stage traditional ACs.
Can a mini-split heat effectively in sub-zero winter temperatures?
Modern 'Hyper-Heat' cold-climate mini-split heat pumps utilize flash vapor injection to deliver 100% rated heating capacity down to -5°F (-20°C) and continue operating down to -15°F to -22°F.